I think I remember R0 being referred to as the Track Capacity record. It was not a constant, but held the remaining capacity after the last formatting write.
Regards, Richard Schuh > -----Original Message----- > From: The IBM z/VM Operating System > [mailto:IBMVM@LISTSERV.UARK.EDU] On Behalf Of Alan Altmark > Sent: Friday, May 20, 2011 7:04 AM > To: IBMVM@LISTSERV.UARK.EDU > Subject: Re: DASD HA & R0 ? > > On Friday, 05/20/2011 at 09:00 EDT, Tom Huegel > <tehue...@gmail.com> wrote: > > Can anyone point me to a doc that has the format of ECKD > Home Address > (HA) and > > Record 0 (R0) records? > > It's odd that the most recent programming reference for ECKD > DASD (IBM ESS S/390 Command Reference, SC26-7298) does not > describe the format of the HA except to say that it is 5 bytes. > > Dragging out an old 3880 book, READ HOME ADDRESS transfers > "the flag, cylinder, and head bytes of the home address > area." I'm assuming that's > of the form FCCHH. I only see a description of flag byte > bits 6-7='10': > Next track defective. > > In that same 3880 book, READ SPECIAL HOME ADDRESS transfers > "the skip control bytes, segment number, physical address > bytes, flag, and identifier bytes (CCHH) of the home address > area" with no further description. > > I'm guessing that detailed HA content is part of the > proprietary disk architecture, but you'd have to raise a > problem to your storage vendor to find out. > > R0 doesn't have any special format except that it is 8 bytes > with KL=0. > > The most r > Alan Altmark > > z/VM and Linux on System z Consultant > IBM System Lab Services and Training > ibm.com/systems/services/labservices > office: 607.429.3323 > mobile; 607.321.7556 > alan_altm...@us.ibm.com > IBM Endicott >
